1. Field of the Invention
The present invention relates to a telescopic lens apparatus having a plurality of lens units, and a camera.
2. Description of the Related Art
Conventionally, image-taking apparatuses such as a small camera which takes pictures using a silver film and a digital still camera which causes an image pickup element such as a CCD to photoelectrically convert an optical image, electrically reads image information and records it in a recording medium such as a memory are provided with a so-called collapse type lens-barrel which is housed in the body of the image-taking apparatus when not in use with its overall length shortened from the length of the lens-barrel when the apparatus is in use for the purpose of improving portability.
There are various proposals of a configuration of a collapse type lens-barrel. For example, in Japanese Patent Application Laid-Open NO. 2000-304999 (Document 1), a collapse type lens-barrel is disclosed. The collapse type lens-barrel performs a magnification varying operation and collapses the entire lens-barrel by rotating a cam member (cam frame) provided with a plurality of cams on its inner surface or outer surface around the optical axis and moving a plurality of lens holding members (lens frames) engaged with their respective cams through a cam pin forward or backward in the direction of the optical axis.
Furthermore, with an increasing number of pixels and miniaturization of image pickup elements in recent years, there is an increasing demand for a lens-barrel having an image-taking optical system with higher performance. There is also an increasing demand for a small image-taking apparatus with a zoom lens of a high magnification varying ratio.
In the lens-barrel proposed in the above described Document 1, a second lens holding member (second lens frame) is guided in the direction of the optical axis by a guide shaft which protrudes from a fixed member (fixed frame) and the inclination of the second lens holding member is suppressed through a sleeve portion of a predetermined length engaged with the guide shaft.
However, the second lens holding member is supported only through the guide shaft and only one end of the guide shaft is supported by the fixed member, and therefore especially when the second lens holding member moves in front of the guide shaft, the guide shaft is easily bent by a force transmitted from the cam member through the cam pin, etc., an inclination of the second lens unit with respect to the designed optical axis of the overall lens system occurs, resulting in a problem that satisfactory optical performance is not acquired.
Furthermore, trying to repress the inclination of the second lens holding member by increasing the length of engagement of the sleeve portion with respect to the guide shaft results in another problem that the presence of the long sleeve portion prevents the full length of the lens-barrel from being fully shortened when it is in a collapsed state.